0.10.0: json_trunc log formatter

What's Changed

Add :json_trunc log formatter by @rgalanakis in #14

Use :json_trunc formatter when configuring semantic logger, such as with Appydays::Loggable.configure_12factor(format: :json_trunc)

SemanticLogger Formatter that truncates large strings in the structured log payload.
If the emitted JSON log is longer than +max_message_len+:

• the payload is walked,
• any strings with a length greater than +max_string_len+ are shortened using +shorten_string+.
  Override +shorten_string+ for custom behavior.
• any key +:stack_trace+ has its array truncated. Stack traces are very large,
  but contain short strings. Override +truncate_stack_trace+ for custom behavior.

Dotenviable: Load env into another hash by @rgalanakis in #13

Allows loading of alternative environments,
usually needed only for testing, but sometimes in other situations (like loading development database urls from a test environment).

Full Changelog: 0.8.0...0.10.0